In an article published in 1912 with the title: “The influence of variations in temperature and blood-pressure on the performance of the isolated mammalian heart”, by F. P. Knowlton and E. H. Starling, from the Institute of Physiology, University College, London, there is disclosed a method by which it is possible to determine the output of the left ventricle under approximately normal conditions, and to vary at will the arterial resistance, the venous pressure, the filling of the heart, or the temperature of the blood supply to the heart. This device is the basis for many later developed afterload devices for determining the output of the heart.
In another article with the title: “The arterial Windkessel” by Nico Westerhof, Jan-Willem Lankhaar and Berend E. Westerhof, published in 2008, a lumped model of a so-called Windkessel model is disclosed.
As discussed in more detail below, the previously known devices have a number of drawbacks, the most striking being that they cannot allow the heart to produce a normal diastole. If the isolated heart model is used as described, no proper heart function is obtained.
Thus, there is a need for a better afterload device, which does not load the heart with a large volume of fluid. In addition, there is a need for a preload device, in which the risk of including air into the fluid flow is minimized or removed. In addition, numerous other improvements are required.